Influence of Aggregation on the Performance of All-Polymer Solar Cells Containing Low-Bandgap Naphthalenediimide Copolymers
Influence of Aggregation on the Performance of All-Polymer Solar Cells Containing Low-Bandgap Naphthalenediimide Copolymers
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DOI：
10.1002/aenm.201100601
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发表时间：
2012-03-01
影响因子：
27.8
通讯作者：
Neher, Dieter
中科院分区：
文献类型：
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作者：
Schubert, Marcel;Dolfen, Daniel;Neher, Dieter
作者提出了高效的全聚合物太阳能电池，其包含两种不同的基于低带隙萘二酰亚胺（NDI）的共聚物作为受体和区域规则的P3HT作为供体。结果表明，这些萘共聚物在特定的有机溶剂中具有很强的预聚集倾向，并且当使用具有大的和高度可极化的芳香族核的合适溶剂时，预聚集可以被完全抑制。由这种非聚集聚合物溶液制备的有机太阳能电池显示出高达1.4%的功率转换效率的显著增加，这主要是由于短路电流的大幅增加。此外，优化的太阳能电池显示出高达70%的高填充因子。共混物吸收光谱的分析揭示了固体P3HT：NDI共聚物共混物中聚合物聚集程度与其光伏性能之间令人惊讶的线性关系。扫描近场光学显微镜（SNOM）和原子力显微镜（AFM）测量揭示了共混物形态的重要信息。结果表明，具有高聚集度和低光电流的薄膜表现出大规模的相分离，形成相当纯的供体和受体域。有人提出，通过抑制NDI共聚物在膜形成的早期阶段的聚集，改进了供体和受体组分的混合，从而允许在供体受体异质结处有效地收获光生激子。
The authors present efficient all-polymer solar cells comprising two different low-bandgap naphthalenediimide (NDI)-based copolymers as acceptors and regioregular P3HT as the donor. It is shown that these naphthalene copolymers have a strong tendency to preaggregate in specific organic solvents, and that preaggregation can be completely suppressed when using suitable solvents with large and highly polarizable aromatic cores. Organic solar cells prepared from such nonaggregated polymer solutions show dramatically increased power conversion efficiencies of up to 1.4%, which is mainly due to a large increase of the short circuit current. In addition, optimized solar cells show remarkable high fill factors of up to 70%. The analysis of the blend absorbance spectra reveals a surprising anticorrelation between the degree of polymer aggregation in the solid P3HT:NDI copolymer blends and their photovoltaic performance. Scanning near-field optical microscopy (SNOM) and atomic force microscopy (AFM) measurements reveal important information on the blend morphology. It is shown that films with high degree of aggregation and low photocurrents exhibit large-scale phase-separation into rather pure donor and acceptor domains. It is proposed that, by suppressing the aggregation of NDI copolymers at the early stage of film formation, the intermixing of the donor and acceptor component is improved, thereby allowing efficient harvesting of photogenerated excitons at the donoracceptor heterojunction.